thanks Swaiba for the quick reply, very much appreciated. It all makes a lot more sense now I searched for manifest.
For anyone else who comes across this I'll explain what I found, for each class ManifestBuilder.php stores in cache a file name manifestClassParse-ExamplePage_php-66d4f5ee00b281254d01a3dc361b71f4 where ExamplePage.php is a class I created. Inside is an array showing how this class is related to another class for example I have pasted Page.php manifest file below. While this doesn't need to be known for daily SS running I find it really interesting how they have built the foundations. Props to the development team
<?php
$classes = array (
0 =>
array (
'className' => 'Page',
'extends' => 'SiteTree',
),
1 =>
array (
'className' => 'Page_Controller',
'extends' => 'ContentController',
),
);
$interfaces = array (
);